If your allowed, why not go along with camera and kit lens and find out what focal length on the zoom gets the photo area coverage you want.You may need somethong bigger or have to do significanr cropping.Anyway could give you a starting point for what you consider most usable focal length.

If you know someone who can allow you access to a theatre even when there is no show on this would probably do equally well,i.e 6 seats back say 80mm focal length ??

Jay D - You won't see the focus points when you just look into the viewfinder. What you DO see when you half press the shutter or press the AF button (on the K10)is a red square indicating which focus point(s) the camera uses to focus. You'll also see the point light up brieflyas you are manually focusing, when the camera thinksthe focus is right.

If you have the camera on auto, it will try to figure what you want to focus on - works pretty well quite often, but can sometimes focus on something you don't want. You'll see the brief flash of red when it focuses and that can tell you if it focused on the right thing. If you have the camera set for center focus, the red light in the center will come on. If you have the camera set to select point, you use the arrow buttons to change the point, and the red sensor indicator will light up briefly to indicate which point you've selected. Does that answer your question?